* {
  box-sizing: border-box;
}

body {
    margin: 0;
    width: 100%;
    height: 100%;
}

#header {
    position: absolute;
    width: 100%;
    height: 10%;
    background-color: black;
}

#header span {
    float: left;
    width: 10%;
    height: 100%;
}

#header .btn {
    margin-top: 10%;
    margin-bottom: 10%;
    color: black;
    cursor: pointer;
}

#header .search {
    margin-top: 10%;
    background-color: white;
    height: 30%;
    placeholder: "text";
}